Aluminum alloy



United States Patent 3,345,159 ALUMINUM ALLOY Laszlo Vilmos Sandor, Henrico County, Va., assignor to Reynolds Metals Company, Richmond, Va., a corporation of Delaware No Drawing. Filed Oct. 16, 1964, Ser. No. 404,515

- 2 Claims. (Cl. 75-146) ABSTRACT OF THE DISCLOSURE An aluminum base alloy containing magnesium (about 1.652.40%), zinc (about 1.501.85%), and manganese (about 0.30-1.0% with more magnesium than zinc (preferably at least 12:1), and up to a fractional percent each of silicon, iron and copper, balance essentially aluminum.

This invention relates to strain hardening alloys of aluminum, and, more particularly, to aluminum-magnesium-zinc-manganese alloys well suited for use in manu facturing can stock and the like. The invention also concerns the manufacture of sheet composed of such alloys.

Wrought aluminum base alloys are known which contain magnesium as the principal alloying addition (the 5000 series, Aluminum Association designation), as well as various aluminum-manganese alloys (3000 series) both without magnesium (such as 3003) and with an addition of magnesium (such as 3004). Also known are zinc-containing alloys (7000 series) which are heat-treatable, such as alloy 7075,- for example, containing zinc as the principal alloying element, with lesser amounts of magnesium and still less copper.

There are also known in the prior art aluminum base casting alloys which include intentional additions of magnesium, zinc and copper, as well as silicon, but in which the amount of magnesium is appreciably less than the zinc content.

In contrast, the instant alloy differs compositionally from alloys previously known by containing magnesium, zinc and managese, with zinc in an amount intermediate the magnesium and manganese contents. It may be characterized, therefore, as an aluminum-magnesium-zincmanganese alloy. The alloy is essentially non-heat treatable, i.e. the amount of zinc being so little that potential hardening constituents are present below their solubility limit following solution heat treatment, even at ambient temperature, and there is substantially no improvement in strength as a result of subsequent aging treatment.

The alloy of the present invention typically contains about 1.65-2.40% magnesium, about 1.50-1.85% zinc, and about 0.30-1.0% (preferably 0.50-.90%) manganese, by weight, balance substantially aluminum. It may also contain up to about 0.20% silicon, 0.30% iron and 0.30% copper. The ratio of magnesium to zinc must be greater than 1:1, preferably at least about 12:1.

The increased amount of magnesium in this alloy compared to 3004, for example, coupled with the intentional addition of a controlled amount of zinc, has been found to provide a distinctive combination of properties and characteristics. For example, the alloy is readily cast; there is no need to homogenize the ingot prior to rolling; heavy rolling reductions are possible, with freedom from edge cracking; cold rolling to a reduction of at least 90% is readily accomplished without intermediate annealing; a relatively bright surface finish is attainable; the maximum tensile strength in condition suitable for can-forming operations is about 55,000 psi, compared to about 35,000 psi. for 3004-H320 material commonly used for that purpose; cans made from the alloy are sufiiciently strong at ordinary wall thickness for carbonaceous soft drinks, which heretofore presented certain problems for aluminum; and cans made of this alloy can resist a bulge pressure twice as great as those of 3004-H320 of similar Wall thickness, so that appreciable reduction in gauge (about 25%) can be realized.

The following examples of the invention, provided for purposes of illustration, are not to be regarded as limiting:

Example 1 An Al-Mg-Zn-Mn alloy was prepared in accordance with the invention, having the following analysis:

The alloy was cast in ingot form, scalped, hot-rolled, to 0.126 inch thickness and cold rolled to about .019 cold working), then stress relieved at 380-385" F. for 8 hours.

The mechanical properties of the resulting sheet are given in Table I.

TABLE I TS(Ks.i.) 47.0 YS(Ks.i.) 40.2 El. percent (in 2") 6.0 Height of Ericksen Cup (mm.) 6.2

Example 2 Sheets were prepared in the manner of Example 1, from alloys A and B having the following analysis:

3 It will be noted that the respective Mg/Zn ratios are about 1.18:1 and 1.06:1. Properties of the resultant sheet stock are shown in Table II.

4 it will be recognized that the invention may be otherwise variously embodied and practiced within the scope of the following claims.

TABLE II Alloy Gauge, Final Thermal Treatment TS (K s.i.) YS (K s.i.) Percent Avg. Bulge Inches El. (2) Fr. (p.s.i.)

3004-H320 .0197 (1) 320 F., 3 hrs 33. 28.6 5. 5 99 .0196 (1) 380 F., 3% hrs 49. 3 41.0 6. 3 150 (2) 350 F 3 hrs 51.2 43. 4 6.0 164 54.1 45.7 6.0 168 55. 7 50.4 6.0 17-5 45.9 39. 5 6.0 135 44. 7 38. 4 6. 2 130 48.1 41.4 5. 3 129 From the results indicated in Table II it is apparent that properties of the alloy fall off as the Mg/Zn ratio approaches unity.

Example 3 Further comparative results using alloys A and B of Example 2 are shown in Table III, based upon evaluation of drawn and ironed 12-ounce cans made from the respective sheet materials.

These typical properties were determined in the circumferential direction relative to the substantially cylindrical can body.

It is noteworthy from the data of Table III that the spread between tensile and yield strengths for the Al- MgZn-Mn alloy of the invention remained about 6000 p.s.i. (even after ironing tantamount to approximately 62% cold work), in contrast to a diflerence of only 3500 p.s.i. for the conventional 3004-H320; and the difference between the respective maximum tensile strengths was still about 20,000 p.s.i. Likewise, the ductility at such high levels of mechanical properties was markedly superior. These characteristics are especially desirable for subsequent cold forming operations such as flanging and double seaming.

While present preferred embodiments of the invention have been described and illustrated by specific examples,

What is claimed is: 1. An aluminum base alloy adapted to making lightgauge wrought articles of improved mechanical properties in work hardened condition, said alloy (a) consisting essentially of aluminum, about 1.65-

2.40% magnesium by weight, about 1.50-1.85% zinc, the magnesium content of the alloy being greater than its zinc content, about 0.30-1.0% manganese, and silicon, iron and copper not exceeding about 0.20% silicon, about 0.30% iron and about 0.30% copper; and

(b) being further characterized by the following properties:

(i) in the form of cold rolled sheet at about .02 gauge, having a tensile strength of approximately 55,000 p.s.i. while retaining suflicient ductility for can-forming operations;

(ii) in work hardened condition of such sheet after a further reduction of about 62% cold work, as typically involved in making a drawn and ironed can body, having a tensile strength about 6,000 p.s.i. higher than its yield strength; and

(iii) in the form of such a can body of wall thickness about .008", having a bulge pressure sufficient to contain carbonated beverages while still retaining ductility necessary for forming operations such as flanging and seaming.

2. An alloy according to claim 1, containing about 0.500.90% manganese and having an Mg/Zn ratio of at least about 1.2: l.

References Cited UNITED STATES PATENTS 2,865,796 12/1958 Rosenkranz 75146 2,985,530 5/1961 Fetzer et al 75-146 3,133,839 5/1964 Thomas -146 3,171,760 3/1965 Vernam et al. 75-l46 DAVID L. RECK, Primary Examiner.

R. O. DEAN, Assistant Examiner. 

1. AN ALUMINUM BASE ALLOY ADAPTED TO MAKING LIGHTGAUGE WROUGHT ARTICLES OF IMPROVED MECHANICAL PROPERTIES IN WORK HARDENED CONDITION, SAID ALLOY (A) CONSISTING ESSENTIALLY OF ALUMINUM, ABOUT 1.652.40% MAGNESIUM BY WEIGHT, ABOUT 1.50-1.85% ZINC, THE MAGNESIUM CONTENT OF THE ALLOY BEING GREATER THAN ITS ZINC CONTENT, ABOUT 0.30-1.0% MANGANESE, AND SILICON, IRON AND COPPER NOT EXCEEDING ABOUT O.20% SILICON, ABOUT 0.30% IRON AND ABOUT 0.30% COPPER; AND (B) BEING FURTHER CHARACTERIZED BY THE FOLLOWING PROPERTIES: (I) IN THE FORM OF COLD ROLLED SHEET AT ABOUT .02" GAUGE, HAVING A TENSILE STRENGTH OF APPROXIMATELY 55,000 P.S.I. WHILE RETAINING SUFFICIENT DUCTILITY FOR CAN-FORMING OPERATIONS; (II) IN WORK HARDENED CONDITION OF SUCH SHEET AFTER A FURTHER REDUCTION OF ABOUT 62% COLD WORK, AS TYPICALLY INVOLVED IN MAKING A DRAWN AND IRONED CAN BODY, HAVING A TENSILE STRENGTH ABOUT 6,000 P.S.I. HIGHER THAN IT YIELD STRENGTH; AND (III) IN THE FORM OF SUCH A CAN BODY OF WALL THICKNESS ABOUT .008", HAVING A BULGE PRESSURE SUFFICIENT TO CONTAIN CARBONATED BEVERAGES WHILE STILL RETAINING DUCTILITY NECESSARY FOR FORMING OPERATIONS SUCH AS FLANGING AND SEAMING. 